afni.nimh.nih.gov

I don't know much about BrainVoyager, but your post several months ago leads me to believe you can create the voi file with 3dmaskdump. There was a posting many years ago with a sample script that basically does just that.

http://afni.nimh.nih.gov/afni/community/board/read.php?1,62086,62090#msg-62090

BrainVoyager itself may very well support converting NIFTI datasets to VOI files too.